A wooden container that can be found in all three games.
First two Games[]
Common Barrel[]
A large barrel.
There appear to be two types of barrels in the first two games (Thief: The Dark Project/Thief Gold and Thief II: The Metal Age), a large on and a smaller one that is about half the size of the big one but they are identical in all other ways. They all are empty and it is not clear what their content would have been. They can be pushes with enough effort and bashed to pieces with the Sword but serve no real purpose. Barrels are lighter than water as some barrels can be seen floating in the Spider cave in "Lord Bafford's Manor" and when a barrel is pushed in water it will sink and slowly ascend back toward the surface and remain afloat. It's even possible to climb on them in this state.
Skull Barrel[]
A barrel containing a skull.
These are identical to the common barrel except for the white skull and cross bones on the side. Similarly it contains no contents and it is not clear what this would have been but it is assumed to be dangerous. Like the common barrel, it has a smaller counterpart, about half the standard size, which is identical in all other respects.
Rotten Barrel[]
A rotten version of the common barrel also comes in a bigger and a smaller size. The texture looks similar to that of an old wooden crate. Unlike most wooden destructibles, these do not produce flinders when destroyed but simply vanish. Although these are barrels, DromEd classifies them as debris along with the Barrel Hoop.
Thief: Deadly Shadows[]
TDS Barrels
Plain barrels exist in Thief: Deadly Shadows as well, but with different properties. All standard TDS barrels are covered and able to roll and a small TDS barrel can be carried and thrown. When destroyed, either by explosives or by landing on sharp objects, they burst into a cloud of dust. Arrows stick into these barrels and can be retrieved from them.
Two medium-sized barrels in the dormitory of the Keeper Compound have the lids removed and are more difficult to push.